The premise of your question is not entirely accurate. While it is true that albinos have historically been portrayed in negative or villainous roles in film and literature, it is not a universal rule, and there have been many instances of albinos being portrayed positively.

Here are a few possible explanations for why this stereotype might exist:

1. Historical Context: Historically, people with albinism have often been subjected to discrimination and stigma in various cultures due to their unique appearance. This discrimination might have influenced the way they were portrayed in media, with negative and villainous roles reflecting societal prejudices.

2. Lack of Representation: Until relatively recent times, there has been a lack of representation of people with albinism in mainstream media. This lack of diverse representation meant that there was an absence of positive counter-narratives to challenge existing stereotypes.

3. Sensationalism: Media outlets sometimes exploit the unique appearance of people with albinism to create sensationalism or shock value, leading to the perpetuation of negative stereotypes.

4. Misconceptions and Misinformation: There are many misconceptions and misinformation about albinism, which can contribute to the perpetuation of negative stereotypes. For instance, some people mistakenly associate albinism with evil, dangerousness, or other negative traits.

Overcoming this stereotype requires conscious effort in the entertainment industry and society to promote accurate representation, challenge harmful stereotypes, and educate the public about albinism. Positive portrayal and representation of people with albinism in various media can help to counter existing stereotypes and foster a more inclusive society.